Aircraft problems?

[harris921]

Just curious as a car mechanic what are planes like to work on? Heavy going? Got to take loads off to access the component you need to change?

Do you change many engines or do you strip them down and repair them? In the car world we no longer change piston rings or bottom ends or lap in valves as the labour rate involved means it's actually cheaper to fit a brand new engine or brand new head. Same with gear boxes really.

Do you get missfires and poor runing faults? Do you carry out compression tests and coolant pressure tests?

Is there alot of component swapping?

 

[Talk Wrench]

Some interesting questions there Harris but the simple answer is that aircraft are nothing like working on a car. The physics involved and maintenance practices have enomous similarities but the truth is that the philosophies of car and aircraft maintenance are poles apart.

Just curious as a car mechanic what are planes like to work on? Heavy going? Got to take loads off to access the component you need to change?

Aircraft can be easy to work on or difficult to work on. This can depend on the type of aircraft and its complexity. Heavy going? Sometimes yes and sometimes no, depending on the complexity of the task. For example, the task could be to top up the hydraulic reservoir or to change a navigation light bulb. The tasks are not complex and can be done quickly and easily. Having to change a hydraulic reservoir is a much bigger job and would require many man hours and lots of checks to put the aircraft back into service. having to rewire a nav light system could take weeks because of the amount of preperation required.

Some components are easily accessible, others are buried deep inside the airframe.

Do you change many engines or do you strip them down and repair them? In the car world we no longer change piston rings or bottom ends or lap in valves as the labour rate involved means it's actually cheaper to fit a brand new engine or brand new head. Same with gear boxes really.

Engines are changed frequently but although the principle of suck, squeeze, bang, blow are the same, a car engine and a jet engine are different kettles of fish.

An engine may be replaced for example due to FOD damage, overtemperature or maybe it's been working okay but is due overhaul. There are many other reasons. Gearboxes are usually sent away with the engine as part of the full assembly

Do you get missfires and poor runing faults? Do you carry out compression tests and coolant pressure tests?

We do get conditions on engines such as overfueling, overtemperature, compresser stall and surges and not misfires as such. On a jet engine, the cooling system is much different to that of a car engine and primarily uses oil,and air. A lot of maths procedures are used to determine the engine efficiency and RPM, inlet and gas temparature are some of the parameters used. A sooty will be able to give you more info. ( I'm avionics myself)

Is there alot of component swapping?

Yes there is. Lots and lots of it.


In a nutshell, it's a completely different world!

TW

 

[enginesuck]

Is it really poles apart ?

Do you as a car mechanic use specialist test equipment to fault diagnose... yes so do we.

Is it easy changing an oil filter - yes , same on a/c

Is it a pain stripping out a water pump on a car - yes, same as probably changing a carbon seal on a rb199 g/box

Changing engines depends on a/c large multi engine a/c engines seem to last a bit longer in my experiance, if your a fast jets they seem to be in and out frequently. Tornado engine change easy as you like. Harrier engine change be prepared to take the wing off first! Nimrod engine change, not too bad but will take a couple of days.

Bear in mind a lot of engine snags can be fixed with component changes in situ and or adjestments of the fuel regulators and airflow control systems.

So once you have sound system knowledge and the requisite hand skills there is not much different i would say, apart from one tiny thing...

if you **** up on a car its not going to drop 30,000 ft to the ground.

Hope this helps.

 

[propersplitbrainme]

Do you get missfires and poor runing faults? Do you carry out compression tests and coolant pressure tests?

Is there alot of component swapping?

Tw seems to have summed it up nicley Harris, but to concentrate on these points, the answer is yes 'in a manner of speaking'.

Missfires don't occur as such because the engine 'spark plugs' only operate when the engine is starting, so the fault you would get would be a failure to start or a slow or what we call 'hot' start where the engine temperature increases dramatically. Exhaust tempearture is an extremenly important parameter with gas turbine engines; overtemp one and you shorten the life or end up changing it.
The engine can do we we call 'surge', this is where the airflow through the compressor gets upset, it can happen for a vareity of reasons, and the flow reverses. This can cause severe damage, spitting combustion gas out the intake and compressor blades as well if its bad enough.
Yes, engine systems are tested with pressure rigs and such like, but not compression tests like a car cylinder, nor coolant pressure because they are air cooled. Testing the engine at the level most RAF technicians operate usually means actually running the thing and then deducing from the resulting RPMs, fuel flow and gas temperature, amongst others, whether it is working or not.
One thing that makes running and testing a gas turbine engine different from a piston engine is that it extremely important to consider the atmospheric conditions on the day you are doing the test. Think about it from basic physics, cold air is thick and dense whilst hot air is thin; a gas turbine engine will turn a lot more easily in hot thin air than it will in cold thick air - as an analgagy think of the difference between trying to stir a spoon in custard as opposed to milk. If you don't take this into consideration you cannot make meaningful comparisons between your test engine's preformance and the correct performance for an engine of that type. Google, Interantional Standard Atmosphere for a deeper explanation.

Hope that helps.

 

[harris921]

Cool, sounds very interesting.

 

[Talk Wrench]

if you **** up on a car its not going to drop 30,000 ft to the ground.

Harris,

Enginesuck has given you the most important statement of all and this principle sticks at the very front of every engineer's mind. Every job has to be done correctly and by the book. There is absolutely no room for error no matter how big or small the job is.

TW

 

[Shugster]

Harris,

Enginesuck has given you the most important statement of all and this principle sticks at the very front of every engineer's mind. Every job has to be done correctly and by the book. There is absolutely no room for error no matter how big or small the job is.

TW

And there's no, "That'll do", mentality. It's either right or it isn't, there's no room for a half done job.

 

[retired real lecky]

And there's no, "That'll do", mentality. It's either right or it isn't, there's no room for a half done job.

so it wont do a trip then!

 

[I Look Like Kevin Costner]

so it wont do a trip then!

It will with an authorised concession!DT_Xtremez_30:

 

[Teh Wal]

Engineering is engineering, the rest just depends on ones attitude and any training undertaken.
DT_Xtremez_14:

 

[tonkaplonka]

I was a time served mechanic before doing 12 years in the RAF working on Tornado and Puma. They are still held together with nuts and bolts but coming across seized and rusted parts that are impossible to shift without heat is something I don't miss in the slightest!
We still do fault finding and diaganosis but as explained earlier the difference between aircraft and cars is worlds apart.
Generally though, I find aircraft easier to work on and some of the better technicians I've worked with have come from the motor trade. You just have to use your brain a bit more and be prepared for reams of paperwork for each job. Aviation pays better as well.
I'm a licensed engineer now working on North Sea Helicopters and I don't miss the motor industry in the slightest.

 

[Rigga]

Apart from Jet engines there are actually some piston engines about the rest of UK (and turbo diesels are just coming into their own too)

"Do you change many engines or do you strip them down and repair them?"

A piston engine on a civil light aircraft can last for up to 15 years if not flown often. At the end of its time it is normally sent to an overhaul shop to be reconditioned and start another 15 years life. Although these may seem like long lives and expensive to turn over (pun - sorry!) the cost of a small aero engine is quite large - last one I did 10+ yrs ago was 9K - and is a major aprt of the cost of an aircraft.

"In the car world we no longer change piston rings or bottom ends or lap in valves as the labour rate involved means it's actually cheaper to fit a brand new engine or brand new head. Same with gear boxes really."

All parts in an aeroengine can be changed and it is often cost effective to do so

"Do you get missfires and poor runing faults? Do you carry out compression tests and coolant pressure tests?"
Yes,Yes,Yes, not often (most are air cooled) "we" also do Exhaust Pipe pressure tests to check for leaks. Heating air is taken from exhaust shrouds - like original VW Beetles did.

"Is there alot of component swapping?"
We are only allowed to swap components if the owner agrees or if the aircraft is part of a single-owned fleet using pooled parts.

Hope this helps
Rigga

 

[Rigga]

As if I'd arranged this to prove the point of how long a piston engine can last!!!!

http://www.caa.co.uk/docs/33/AIRCOM200911.pdf

Paragraph 2.2 refers!

 

[185]

As if I'd arranged this to prove the point of how long a piston engine can last!!!!

http://www.caa.co.uk/docs/33/AIRCOM200911.pdf

Paragraph 2.2 refers!

i remember training on leonides 9 cylinder radial engines early 70s as an appo
raf holton work shops. dont tell me thay are still going.

 

[Rigga]

i remember training on leonides 9 cylinder radial engines early 70s as an appo
raf holton work shops. dont tell me thay are still going.

185,
From the looks of it - you could've be the last one to strip this beastie!

 

[Ex-Splitter and Proud]

185,
From the looks of it - you could've be the last one to strip this beastie!

They were still being stripped an played with at Halton in 1977, when I left. My guess is that they were probably still there through the early 80s (ask propersplitbrainme - he's a fcuking smally!)